The State Government has been threatened with legal action over its decision to slash the solar feed-in tariff scheme.

The move, which it is estimated will save the Government $35 million, will affect more than 75,000 households that installed solar power before mid-2011.

They'll now get 20 cents for every unit of power they feed back into the electricity grid, despite signing 10-year contracts at the higher rate of 40 cents.

Callers to the ABC's Mornings Program have vowed to take part in a class action against the government for breach of contract.

But the Treasurer Troy Buswell says he is not worried.

"The advice we've had is that what we're doing is allowable within the constraints of the contracts," he said.

"I understand people are going to be far from pleased with the outcome, but we have a broader responsibility to the totality of the community."

The Sustainable Energy Association's is also upset by the move.

The Association's Kirsten Rose says the Government has broken its promise to keep the feed-in tariff at a set rate for 10 years.

"Now after two-and-a-half, three years, the government has decided to wind that back and that is a big disappointment and it's going to leave some people in a bit of a financial hole unfortunately," she said.

"The Sustainable Energy Association is disappointed to say the least and consider it a pretty massive betrayal of public trust by the State Government."